Apple has always focused on cpu, battery life, form factors and other features in their computers before graphics, while everybody else tends to put them aside only for the sake of graphics.
Bottom line, even though they're not the strongest mobile gpus on the market, they're not the weakest either-- apple are not marketing the macbookpros as purely gaming laptops, they choose their own options in what they think makes for the overall best computer. The best example I could give you would be my pair of headphones. They have extremely bright and full treble, great mids, have an open ear design and have enormous soundstage-- they make for a very great listening experience. But due to all those great things, they lack in bass reproduction a bit, so bassheads would be quick to turn their head up to them.
What I'm getting at is that you should buy something else if you don't like what apple offers in the macbooks pros. There are plenty of laptops out there that undoubtedly focus only on gaming performance, but you'll have a fun time with their 2 inch thicknesses and 30 minute battery lives.